The present invention relates to fluid-flow control devices. The invention is particularly useful as drip-irrigation emitters and is therefore described below with respect to this application.
Various types of drip-irrigation emitters are known for supplying water, with or without additives, directly to the root zone of the plants at a slow controlled rate. One type provides an opening of small cross-sectional area to produce the slow output flow, but a main drawback of this type is its high sensitivity to clogging. Another type provides a long or labyrinth passageway to produce the slow output flow; this type is probably the most popular at the present time, but the known designs are still not completely satisfactory particularly because of sensitivity to clogging, difficulty to remove clogging particles, and sensitivity to line-pressure variations. A further known type of drip-irrigation emitter provides a control member movable towards and away from an opening to control the output flow, but the known designs of this type are also not completely satisfactory particularly in applications involving very low line pressures in the supply pipe.
An object of the present invention is to provide a novel fluid-flow control device of the above-mentioned third type, which device is particularly useful as a drip-irrigation emitter.